Recently, linear motion guide units expected to work with maintenance-free condition for lubrication are becoming more used in any parts moving in a reciprocating manner in a diversity of machines. Extensively various applications to machines has needed a diversity of linear motion guide units that could ensure the maintenance-free operating conditions for lubrication.
In the commonly assigned Japanese Patent Laid-Open No. 2003-90338, there is disclosed a linear motion guide unit in which tubular connectors are installed to communicate turnaround passages with their associated return passage. With the prior linear motion guide unit constructed as recited earlier, the tubular connectors are each made up of a connector part of a spacer arranged on any one of lengthwise opposite ends of a return passage member lying within a lengthwise bore in a carriage, and a complementary connector part lying in any one of lengthwise opposite end caps, making the return passage and the associated turnaround passages flush with one another to finish the recirculating circuit with causing no gap at the connection between the return passage and the turnaround passages, thereby making sure of allowing the rolling elements to transfer smoothly from the turnaround passages to their associated return passage and also from the return passage to the turnaround passages in a circulating manner. Moreover, the return passage member is made of sintered resinous material of cellular texture adapted to retaining lubricant therein to continue applying an adequate lubricant around the rolling elements.
With the prior linear motion guide units recited earlier, nevertheless, the return passages are made in a slider in a way lying horizontally in parallel with load-carrying races at sidewise faraway areas. This geometry of the return passages needs making the slider larger in widthwise measurement. Meanwhile, advanced technology has come to hope any linear motion guide unit of miniaturized construction even though there are used rolling elements larger in diameter than conventional ones to have high load capacity. However, it still remains a further challenge to the linear motion guide unit miniaturized as recited earlier to continue supplying any lubricant to the rolling elements with substantially free of maintenance for lubrication.